Dynamic frequency shift in photonic crystal resonators and slow light waveguides

The dynamic frequency shift of the optical pulse can be obtained if the refractive index of the guiding structure is switched while the pulse is inside the structure. We have developed a co-propagating scheme where switching is obtained by a second pulse which generates free carriers into a silicon waveguide and thus shifts refractive index by up to 0.01. The interaction was studied in two systems. First, system based on a photonic crystal heterostructure cavity was considered which was excited at the resonance frequency by the signal and then switched by the second pulse at the frequency of the pass band. In the second system two pulses were propagating in a slow light waveguide. Two pulses with different group velocities could overtake each other inside the structure. In both system theoretical models were developed to explain expected frequency shifts and compared to the experiment.